A conventional 35 mm film cartridge, such as manufactured by Eastman Kodak Company comprises a light-tight housing and an unexposed filmstrip. The filmstrip is supported in a roll on a rotatable spool inside the light-tight housing and has a film leader that protrudes outwardly through a light-trapping slit in the housing. A forward-most portion of the film leader has a reduced width as compared to the remainder of the filmstrip.
A typical camera intended to be used with the conventional film cartridge comprises a cartridge receiving chamber, a film take-up chamber, and a backframe opening between the cartridge receiving chamber and the film take-up chamber at which successive sections of the filmstrip (except for the protruding film leader) are to be exposed. To load the film cartridge into the camera, a rear door of the camera is opened to uncover the film take-up chamber, the backframe opening, and the film take-up chamber. Then the film cartridge is placed in the cartridge-receiving chamber and the protruding film leader is positioned over the backframe opening. The forward-most reduced width portion of the film leader rests on a film rail alongside the backframe opening to be engaged by a sprocket that protrudes out of an opening in the film rail. When the rear door is closed, the sprocket is rotated in engagement with the forward-most reduced width portion of the film leader to thread or advance the forward-most reduced width portion of the film leader into the film take-up chamber. See prior art U.S. Pat. No. 4,397,535, issued Aug. 9, 1983.